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Activities/Turtle Art/Under the hood: Difference between revisions

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'''Note:''' As of Version 106, there is also support for plugins. If you can use the plugin mechanism to add support for additional devices, e.g., Arduino, or for making modifications such as are described below without making changes to the standard code base. (The advantage to the latter is that your changes will remain intact even after you upgrade to a newer version.)
'''Note:''' As of Version 106, there is also support for plugins. If you can use the plugin mechanism to add support for additional devices, e.g., Arduino, or for making modifications such as are described below without making changes to the standard code base. (The advantage to the latter is that your changes will remain intact even after you upgrade to a newer version.)


taconstants.py contains the constants that by-in-large determine the behavior of Turtle Art. Notably, the block palettes are defined below. If you want to add a new block to Turtle Art, it is generally a matter of modifying some tables below and then adding the primitive to talogo.py. For example, if we want to add a new turtle command, 'uturn', we'd make the following changes:
The tabasics.py file contains the constants that by-in-large determine the behavior of Turtle Art. Notably, the block palettes are defined
below. If you want to add a new block to Turtle Art, you could simply add a block of code to that file or to turtle_block_plugin.py,
which contains additional blocks. (Even better, write your own plugin!!)


(1) We'd add 'uturn' to the PALETTES list of lists:
Adding a new palette is simply a matter of:
    palette = make_palette('mypalette',  # the name of your palette
                          colors=["#00FF00", "#00A000"],
                          help_string=_('Palette of my custom commands'))


PALETTES = [['forward', 'back', 'clean', 'left', 'right', 'show',  
For example, if we want to add a new turtle command, 'uturn', we'd use the
              'seth', 'setxy', 'heading', 'xcor', 'ycor', 'setscale',
add_block method in the Palette class.
              'arc', 'scale', 'left', 'top', 'right', 'bottom', 'uturn'],
    palette.add_block('uturn', # the name of your block
            ['penup','pendown', 'setpensize', 'fillscreen', 'pensize',...
                      style='basic-style', # the block style
                      label=_('u turn'), # the label for the block
                      prim_name='uturn', # code reference (see below)
                      help_string=_('turns the turtle 180 degrees'))


(2) Then we'd add it to one of the block-style definitions. Since it takes
    # Next, you need to define what your block will do:
no arguments, we'd add it here:
    # def_prim takes 3 arguments: the primitive name, the number of
    # of arguments, 0 in this case, and the function to call, in this
    # case, the canvas function to set the heading.
    self.tw.lc.def_prim('uturn', 0,
        lambda self: self.tw.canvas.seth(self.tw.canvas.heading + 180))


BASIC_STYLE = ['clean', 'penup', 'pendown', 'stack1', 'stack2', 'vspace',
That's it. When you next run Turtle Art, you will have a 'uturn' block on the 'mypalette' palette.
    'hideblocks', 'showblocks', 'clearheap', 'printheap', 'kbinput', 'uturn']


(3) Then we give it a name (Note the syntax _('string to be
You will have to create icons for the palette-selector buttons. These
translated') used by the language-internationalization system; also
are kept in the icons subdirectory. You need two icons:
note that the name is an array, as some blocks contain multiple
mypaletteoff.svg and mypaletteon.svg, where 'mypalette' is the same
strings.):
string as the entry you used in instantiating the Palette class. Note
 
that the icons should be the same size (55x55) as the others. (This is
BLOCK_NAMES = {
the default icon size for Sugar toolbars.)
...
    'uturn':[_('u-turn')],
...
              }
 
(4) and a help-menu entry:
 
HELP_STRINGS = {
...
    'uturn':_('change the heading of the turtle 180 degrees'),
...
              }
 
(5) Next, we need to define it as a primitive for the Logo command
parser (generally just the same name):
 
PRIMITIVES = {
...
    'uturn':'uturn',
...
            }
 
(6) Since there are no default arguments, we don't need to do anything
else here. But we do need to define the actual function in talogo.py
 
DEFPRIM = {
...
    'uturn':[0, lambda self: self.tw.canvas.seth(self.tw.canvas.heading+180)],
...
          }
 
That's it. When you next run Turtle Art, you will have a 'uturn' block
on the Turtle Palette.
 
[[Image:TAuturn.png|300px]]
 
Adding a new palette is simply a matter of: (1) adding an additional entry to PALETTE_NAMES; (2) new list of blocks to PALETTES; and (3) an additional entry in COLORS. However you will have to: (4) create icons for the palette-selector buttons. These are kept in the icons subdirectory. You need two icons: yourpalettenameoff.svg and yourpalettenameon.svg, where yourpalettename is the same string as the entry you added to the PALETTE_NAMES list. Note that the icons should be the same size (55x55) as the others. This is the default icon size for Sugar toolbars.
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